Google said Tuesday it was going direct to consumers again, selling the Galaxy Nexus smartphone on Google Play for $399. The unlocked smartphone will also run the Google Wallet mobile payment app.

Currently, only Sprint is supporting Google Wallet through its own version of the Galaxy Nexus device, as well as the new LG Viper 4G and LG Optimus Elite. Sprint originally had Google Wallet in September on the Nexus S.

Google Wallet will also be available on the LG Optimus Elite from Virgin Mobile, Google said in a blog post.

While Google Wallet first emerged eight months ago, adoption of the mobile payment technology has been slow. A Google spokesman recognized that fact.

"It's still very early days for mobile payments and we know [it] will take time to building a new mobile commerce ecosystem, but we're very committed to this goal and are encouraged by the progress we've made to date," Google spokesman Nate Tyler said by email.

Tyler said Google has been encouraged by a recent Pew poll that found 65% of respondents believe that using a smartphone as a form of payment will become widely adopted by the end of the decade.

The study, dated April 17, was based on an online sample of 1,021 Internet users and experts and was conducted by Pew Research Center and Elon University's Imagining the Internet Center.

Many mobile payment experts credit Google for moving ahead with mobile payments despite some public concerns about security with such systems. Mobile payments using NFC chips inside phones are popular in countries such as Japan, South Korea and China, especially for transit fares and small retail purchases. Adding more NFC phones is seen as critical to U.S. adoption.

In addition to Google's work with Sprint on mobile payments, Isis, a joint venture of AT&T, Verizon Wireless and T-Mobile USA, is set to launch mobile payments this summer in the U.S.

Google's Galaxy Nexus phone supports Google Wallet on Sprint and in its unlocked version, but notably not on Verizon's version of the Galaxy Nexus.

This new unlocked and contract-free Galaxy Nexus is a GSM phone that can be used on T-Mobile or AT&T.

Google is also working to encourage merchants to support mobile wallet marketing, and recently posted deals for free merchandise at select drugstores in New York City, among other promotions mentioned on its blog.